Precision radio remote-control system



March 9, 1948.

E. L. ROCKWOOD 2 431558 PRECISION RADIO REMOTE CONTROL SYSTEM FiledMarch 12, 1943 AN TEA/NA 2 Sheets-Sheet l Inventor 1% l. Focirwaad y WWZ? M 5 E. L. ROCKWOOD PRECISION RADIO REMOTE CONTROL SYSTEM 2Sheets-Sheet 2 March 9, 1948.

Filed March 12, 1945 Awe/WM AMPLI FIE/F I M I F BATTERYl AMPLIFI RInventor L. EOCFJWdOd y (ma W Em Patented Mu. 9, 1948 PATENT OFFICEPRECISION RADIO REMOTE-CONTROL SYSTEM Edgar L. Rookwood, Berkeley,Calif.

Application March 12, 1948, Serial No. 478,947

2 Claims. 1

This invention relates to remote control systerns and it has for itsobject to provide a system of the character indicated in which thecontrol at the remote point is eiiected by means of two variablefrequencies, transmitted through a communication channel of any type,whose variations are interrelated and always occur in oppositedirections. If, for instance, theamplitude of one of the frequenciesincreases, the amplitude of the other will decrease, the aggregate sumof both being however a constant factor.

With this object in view the invention :mainly resides in a system ofthe type above described with a receiver which is capable of translatingthe variation imparted to the two frequencies in opposite directionsinto a mechanical, preferably rotational movement proportional to thevalue of the difference. The means for effecting such translation maycomprise a filter system for separating the frequencies, and a system ofcoils opposing each other on which the frequencies, after duerectification and amplification, may act. The coils when actingconiointly on a core which is common to them will clearly impart amovement to the core which is proportional to the diflerence of theamplitudes of the two oscillations which, after transformation andamplification, energize the two coils. Said movement may then be useddirectly or indirectly to control the movement of a rotating part drivenby a local source power. The latter movement is therefore stillproportional to the diflerence between the variations oi the amplitudesof the frequencies.

The invention is illustrated in the accompanying drawings showing onemodification thereof. It is however to be understood that thismodification is to be regarded as an example illustrating the principleon which the invention is based and the best modein which this principleis applied. It does not represent the sole modes oi. application of theinvention.

In the drawing:

Figure 1 is a diagrammatic view of a transmitter of some well known typewith two different modulation systems, whose control is interrelated.

Figure 2 is adiagrammatic-view of a receiver station, embodying remotecontrol means operated by the interrelated variation of two receivedfrequencies.

Figure 3 is a diagrammatic elevational view of the mechanicalarrangement reproducing the movement transmitted through thetransmission channel.

The system according to the invention may be carried into efiect withany type of communica- 5 tion system capable of transmittingoscillations. The system used to illustrate an example is a radiocommunication system the transmitter of which is shown in Figure 1. Thetransmitter itself may be of any approved type and need not bedescribed. In order to adapt it for the purposes of the presentinvention it is provided with two modulation tubes M1 and M2, forproducing the modulation of the carrier wave. The modulatingoscillations according to the invention have to be controlled orregulated simultaneously as they are interrelated. In the example shownthe amplitude of these oscillations is regulated by means of the controlgrids G1, Ga of the modulation tubes. The interrelation of the variationof the modulating oscillations which is obtained in the tubes M1 and M2,is produced by providing each grid circuit with a potentiometer P1 andP2, respectively these potentiometers being operated by a common shaftC. When this shaft is rotated in one direction the potentiometers are sooperated that the resistances vary or change in opposite directions.This means that if the resistance in the circuit of grid G2 decreasesthe resistance in the circuit of grid G1 increases and vice versa. It ispreferable to wind the potentiometers in such a way and to use suchfixed resistances that the amplitude of the oscillation in the output orplate circuits of the modulation tubes M1, M2 have an aggregate sumwhich is permanently constant, each increase of the amplitude in-onecircuit being just compensated by the decrease of the amplitude producedsimultaneously in the other circuit. I

The shaft 0 operating the-two potentiometers may be provided with ahandle J which serves as the remote control handle. Every movement ofsaid handle, as will be clear from the above, produces a variation ofthe resistance in the grid circuits of the tubes M1 and M2 and thereby avariation in the output circuits of said tubes which are interrelated inthe manner above indicated.

A carrier wave modulated by the two interrelated modulating frequenciesis radiated through the aerial of the transmitter and is received by theantenna 24 of the receiver shown in Figure 2.

The receiver is a standard receiver which is however adapted to separateagain the two interrelated frequencies, which have been trans assuresmitted. The carrier wave with these two fre= quencies after beingreceived is amplified and demodulated in the demodulator 25 of the re=ceiver. The resulting oscillation will be a oom= bination of the twofrequencies.

In order to separate them the demodulator as of the receiver isconnected with the two filter circuits F; and F2, which are so tunedthat each filter passes merely one of the frequencies con= tained in thecombination. As the filters fh an A. C. of the desired frequency arectifier R1 R2, respectively, is arranged behind each filter to convertthe output into a. pulsating D. C. which may be further amplified by theamplifiers 22. 2! arranged in the output circuits of the rectiflers R1and R2.

The rectifier and amplifier arrangements R1 R2, 22,, 2| are connectedwith the energizing cir cults 32, 83 of solenoid magnets B and A,respec= tlvely, which are aligned and are wound in opposite directions.The battery 85 which may also form the B battery of the amplifiers 2iand 22 provides the solenoid circuits 88 and 82 with cur= rent, whencurrent is passing through the amplifier. Such a passage occurs. as willbe easily understood whenever the filter circuit carries a current andthe current passing through the cir cuits 3-3, r32 will therefore beproportional to the amplitude of the frequency which has passed thefilter and has been rectified in one of the rectal tiers Rt R2 by virtueof the connection of the plate of the latter with the control grid ofthe amplifier. It will thus be clear that the energizing current of eachsolenoid magnet A, B will be proportional to the amplitude of one of theosciilations received.

Both solenoid magnets are encircling a com mon core piece C, which isaxially movable along the common axis of the solenoid magnets. The

position occupied by the core is determined by b the energization of thesolenoid magnets and it will therefore correspond exactly to thedifference between the amplitudes of the two oscillations or, whenreference is made to Figure l, to the posi tion of the hand lever Jdetermining the position of the potentiometer arms. The position of thecore therefore reproduces exactly the amplitude difierence between thefrequencies and the position of the lever J in the transmitting station.

For the purpose of exercising a remote control it is, as a rule,necessary to produce an angular or rotational'movement which reproducesthe movement of the control lever J of the transmitter and which iscapable to overcome a noteble resistance or to exercise some power sothat a local source of power has to be introduced. This translation ofthe movement and introduction of a local source of power is obtained bymeans of the mechanism shown in Figures 2 and 3. This mechanism consistsin an electric motor M driving a disk G by means of a gear train 21. Asa rule a gear train with a high ratio of transmission (for instanceabout 400:1) is necessary. The disk G is of insulating material andcarries two metal plates D and E in the form of a, quadrant. These metalquadrants cooperate with brushes H, H each of which is connected with acircuit containing a special battery I, I or other source of currentrespectively. The batteries are capable of driving the motor M and areconnected with the brushes with opposite poles. Therefore the negativepole will for instance be connected with brush H and quadrant E, whilethe positive pole of battery I is con- Bill) till) ference between thenected, for instance, with brush H and sent D. The two other poles ofthe batteries are connected with each other and with one of the @8818 Kof @116 motor M. A, Di. 1 fie Mir-,1 of the motor is connected withbrush F which is mounted on the movable core C and which is sliding onthe face col the disk.

The motor M is preferably provided with a permanent rinetic field sothat it is reversible and changes its direction oi rotation when thedirection of the current flowing through its ar mature is reversed. Thetels K in this case are connected with the collector brushes. It willalso be clear that the direction of rotation of the motor will depend onthe loattery I, l,

which is connected with the motor by means of brushes H, H and br F.

The operation of the arrangement will be readily understood from theforegoing description..

Assuming the handle J to be the control bar to be moved in order toexercise the remote con-= trol, it will be clear that its movement willchange the amplitude of the two modulating frequencies. The sum of theseamplitudes of the two frequencies as has been stated before, ispreferably constant. Therefore the carrier wave is modu= lated with acombined oscillation containing the two interrelated frequencies. Themodulated carrier wave is received on the moving or stationary object tobe controlled is demodulated and the combined oscillation which is theresult of such demodulation is decomposed into its com ponentfrequencies by the passage through filters F1 and E2. The oscillationscoming from said filters are rectified in rectifiers R1 and R2 and areamplified and energim the coils A and B respectively. If they happen tobe of equal amplitude the core will stay in the center as the magneticactions of the coils A and B on the core are equal. When the amplitudeof one of the frequencies is larger than the other, the core will bemoved to one side. Thereby the brush F is moved to one side and closesthe circuit of the motor M in a definite direction. The motor M isenergized in one direction corresponding to the polarity of the batteryI or I and rotates the disk G until brush F leaves the quadrant. At thispoint the motor is stopped. With the motor the crank or lever N is movedwhich effects the remote control on the controlled object.

It will therefore be clear that the movement of the brush F and core Cto the left or right in Figure 2 determines the direction of rotation ofthe motor and the extent of the movement of this brush determines theextent of the angular mo= tion of the disk and of the controlled leverN. On the other hand the extent of the movement of the brush F and core0 depends on the difamplitudes of the two frequencies and is thereforedependent on the extent to which the lever J Was moved.

It will also be clear that the motor M furnishes the power which isrequired to move the controlled lever to the angular position which isde-= termined by the cooperation of the disk G and the brush F.

Attention may finally be drawn to the fact that the use of twofrequencies for efiecting a remote control is by far preferable to theuse of a single frequency in most cases and is indispensable in thosecases in which a moving object such as an airplane, car, boat or thelike is controlled by a remote control system. If merely one frequencyis employed the movement of the core, for in= stance, is controlled by asingle coil which in this case has to cooperate with a spring or asimilar return means. As this return means exercises a constantinfluence such as a constant pull or push, the relation of thisinfluence or force with respect to the magnetic force pulling the coreis variable with. the distance of the controlled oillost from thecontrolling station which influences the amplitude of the oscillationreceived. According to this invention however, the influence due to anychange in the amplitude of the receiver is eliminated as merely thedifference between the amplitudes of the two modulating os=- cillationswhich is solely dependent on the posi tion of the handle, determines theposition oi the core and thereby the position oi the controlled lever.

It will be clear that the specific arrangement rlescriioeo may hesuhiectecl to modifications without aflectirig essence of the invention.Moreover nncier soeclal circumstances, for instance, where no localsource oi power is neces-= sary to more a controlled member thearrangement introducing the lccol motoric power may he rlispensecl with.

I claim:

l. A remote control system in which control is effected by means of twofrequencies whine ampli tudes are varies iolntly in opts directions withthe amplitude or one frequency decreasing while the amplitude oi theother increases their sum remaining at a constant value, and which comprises a receiver, demodulation means therein, a filter system.comprising: a pair o1 filter circuits. each circuit tuned to one olthetwo frequencies received for separating the same. a rectifierarrangement in each filter circuit and a pair of solenoid coils, eachcoil connected with one of the filter circuits and operated by therectified filter currents, a common movable core operated by the saidsolenoid coils, and moved in proportion to the energizatlon of the coilsand translation means tor transforming said reeiprocotin: movement ofthe core into proportionate rotational 2 1i. remote control system whichcontrol is efiecterl by means oi two frequencies where ampli tucles arevaried jointly in opposite directions with the amplitude of onefrequency decreasing while the amplitude of the other increases theirsum remaining at a constant value, and which coreprises a receiver,demodulating means therein a filter system, comprising a pair or" filtercircuits, each circuit tuned to one of the two frequencies r ceived iorseparating the same, a rectifier arrangement and means for amplifying:the rectifierl circuits in each filter circuit, a pair oi alignedsolenoid coils opposing each other, each coil cor. nested with one ofthe filter circuits, a movable core in common to both solenoid coils andadapted to be shifted by the some in proportion to the relativestrengths of the amplitudes oi the two above mentioned frequenciesreceived, and a translation device for translating the movement of thecore into a rotating motion comprising contact arms fixedly mounted onsaid core, a retatable disc carrying contact segments in opera tiveconnection with said contact arm, a shaft driven by said disc, anelectric reversible motor for driving said disc are shalt operative clrsuite for said electric motor controller by the said contaotor arm andsegments,

REFERENCES CHER The following referenow are of record in the file ofthis patent:

UNITED s'rs'rns PATENTS Number Name Date 1,798,592 Davis Mar. 31, 19312,003,240 Brockstedt May 28, 1985 2,087,432 Beverage Jan. 12. 1937 42,245,347 Koch June 10, 1941 FOREIGN PATENTS Number Country Date 884,825Great Britain Dec. 9, 1932

